Recently, a study on realization of haptic feedback through a touch screen or a touch pad of a small mobile terminal has been actively carried out.
A vibrator is mainly used in order to provide the mobile terminal with the haptic feedback. The vibrator employs a solenoid principle.
In the vibrator using a solenoid, magnetic force generated is proportional to the number of coils wound on a bobbin and the intensity of current.
Therefore, the vibrator using the solenoid has a problem in that the enhancement of vibration power due to an increase in the intensity of magnetic force inevitably leads to an increase in its volume or power consumption.
Thus, it is required to develop a new vibrator which can increase the vibration power, can be small and also can have low power consumption.
Further, in a conventional vibrator, for example, as described in Korean Patent Laid-Open No. 2001-0108361 in which a piezoelectric element is coupled to a flat vibrating plate supported by a spring, an elongated vibrating plate is needed to obtain higher vibration. In case that a length of the vibrating plate becomes longer, space expansion is inevitable, and thus there is a disadvantage to a compact electronic unit applied to the vibrating plate.
Furthermore, in Korean Patent No. 10-1016208, there is disclosed a hybrid actuator using a vibrator.
FIG. 1 is a side cross-sectional view of a conventional actuator using a vibrator.
As shown in FIG. 1, the conventional actuator includes a vibrator 11, 12 which generates vibration according to the intensity of power; a lower plate 20 which is disposed at a lower side of the vibrator 11, 12 so as to be spaced apart from the vibrator 11, 12 and also which has its own elastic characteristic; an electromagnetic force generator 30 which is disposed between the vibrator 11, 12 and the lower plate 20 so as to vibrate the lower plate 20 through electromagnetic force generated by electromagnetic induction; and a fixing means 40 which fixes one end of the vibrator 11, 12 and one end of the lower plate 20 so that the vibrator 11, 12 and the lower plate 20 can be vibrated in the state of being spaced apart from each other.
Detailedly, the vibrator 11, 12 is comprised of a vibrating part 11 and a piezoelectric element 12.
The vibrating part 11 is a plate type elastic member which can be vibrated upward and downward.
The piezoelectric element 12 is a piezo-actuator which is longitudinally expanded or contracted according to the intensity of power supplied.
The piezoelectric element 12 is installed at one side of the vibrating part 11 so as to be expanded or contracted, thereby vibrating the vibrating part 11 up and down.
However, in the conventional actuator using the vibrator 11, 12, if a strong impact is applied thereto due to various factors such as user's carelessness and falling test, there is a problem in that the vibrating part 11 exceeds the elastic limit and is plastic=deformed, thereby being in the inoperable status.